1. Field of the Invention
The present invention relates to a method, an apparatus, and a program for detecting faces, which are included in detection target images.
2. Description of the Related Art
Correction of skin tones in snapshots photographed with digital cameras by investigating color distributions within facial regions, and recognition of people who are pictured in digital images obtained by digital video cameras of security systems is being performed. In these cases, it is necessary to detect regions (facial regions) of unspecified sizes within digital images that correspond to people's faces. For this reason, various techniques have been proposed, for detecting faces of various sizes from within images.
For example, Japanese Unexamined Patent Publication No. 2004-133637 discloses a method for detecting faces of different sizes. In this method, a plurality of scaled images having different sizes that represent a detection target image are generated, based on the detection target image. Partial images of a uniform size are sequentially cut out from the scaled images, by shifting the position of the cutout across the entirety of each of the scaled images. Correlative values, representing the likelihood that the subject of the partial image is a face, are calculated for each partial image. Faces included in the detection target image are detected by judging whether the partial images represent faces, based on the magnitudes of the correlative values. According to this method, judgments are performed regarding each of the partial images, which are sequentially cut out from the scaled images. Therefore, faces can be detected with comparatively high accuracy.
However, it is necessary to perform judgments for each of the partial images, which have been cut out from each of the scaled images, in the above method. Therefore, the amount of data to be processed is great, and there is a problem that face detection requires a long amount of time.